Note: Descriptions are shown in the official language in which they were submitted.
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BCF/RCC/ds 16550
SERVO CONTROLLED GLASS GOB DISTRIBUTOR
The present invention is directed to manufacture of Qlass
articles such as containers, and more particularly to an improved
method and apparatus for distributing gobs of molten glass among a
plurality of mold stations or sections.
Background and Summary of the Invention
Glass containers are conventionally formed in a machine
that comprises a plurality of sections, in each of which there are
one or more blank or parison mold cavities and transfer mechanisms
that are synchronized with each other. This machine. called an
individual section or IS machine, receives glass in the form of
discrete mold charges or gobs. Molten glass from a furnace is cut
into individual gobs, which are fed to a gob distributor. The purpose
of the gob distributor is to distribute the gobs to the individual
sections of the IS machine in the appropriate sequence in such a way
at the glass gobs simultaneously arrive at the mold cavities in each
section in sequence. U.S. Patent Nos. 3,585,017 and 3.597,187, and
patents noted therein, illustrate the general technology.
U.S. Patent No. 2,859,559 discloses a gob distributor
construction in which a scoop is disposed beneath a gob shear mechanism
for receiving molten gobs in sequence, and is coupled by a shaft to
a motor for feeding the individual gobs to spaced chutes or troughs.
Each trough leads to the initial mold cavity of an associated section
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of an IS machine. Each cavity of the IS machine has an associated
trough, and the scoop feeds gobs to the individual troughs in an
appropriate sequence. U.S. Patent No. 3,597,187 discloses a gob
distributor in which a plurality of scoops each have an upper end
disposed beneath an associated gob discharge, and a lower end disposed
to swing through an arc adjacent to a corresponding plurality of
troughs. Each scoop is carried by a scoop support frame, which is
in turn is coupled to a drive shaft. The multiple drive shafts are
coupled to a gear transmission drive, in which the shafts are
conjointly driven through associated gears by a single motor. Although
this transmission drive arrangement maintains proper synchronism
among the scoops, a problem arises when it is desired to change the
number of scoops. An entirely new transmission drive is required.
A general object of the present invention is to provide a
glass gob distribution system and method in which gob distribution
scoops may be readily added, deleted or inactivated without requiring
redesign or replacement of the entire scoop drive structure. Another
and more specific object of the present invention is to provide a
glass gob distribution system and method for a multiple-cavity IS
machine in which the scoop for each cavity is mechanically independent
from the scoops for the other cavities, and in which scoop position
and motion profile may be readily electronically adjusted
independently of the other scoops of the distribution system.
A molten glass gob distributor for a glass article
manufacturing system in accordance with the present invention includes
a plurality of gob discharges, and a plurality of scoops for receiving
gobs from each such discharge and distributing the gobs among a
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plurality of troughs or chutes leading to associated molds in a
multiple-cavity IS machine. Each scoop is mounted to rotate about
a fixed axis with the upper end remaining positioned beneath the
associated gob discharge while the lower end swings through an arc
adjacent to the associated troughs. A plurality of electric motors
are individually coupled to each associated scoop for selectively
and individually rotating the scoops. The electric motors are all
connected to a motor controller for synchronizing operation of the
motors and rotation of the scoops to each other and to operation of
the forming machine. Preferably, the motors comprise electric servo
motors each individually coupled to a single associated scoop, and
the motor controller comprises an electronic servo motor controller
operatively coupled to each servo motor and synchronizing operation
thereof by means of a synchronizing input from the forming machine.
Brief Description of the Drawings
The invention, together with additional objects, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
FIG. 1 is a fragmentary perspective view that illustrates
a molten glass gob distribution system in accordance with one presently
preferred embodiment of the invention;
FIG. 2 is a functional block diagram of the gob distribution
system illustrated in FIG. 1;
FIG. 3 is a functional block diagram of each motion
controller illustrated in FIG. 2; and
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FIG. 4 is a graphic illustration of motion profile for
each scoop, illustrating sequence of delivery of mold charges or
gabs to the eight sections of an IS machine.
Detailed Descri tion of Preferred Embodiment
FIG. 1 illustrates a gob distribution system 10 in
accordance with one presently preferred embodiment of the invention
as comprising three arcuate scoops 12,14,16 each having an upper end
positioned beneath an associated glass gob discharge orifice 18,20,22.
Each scoop 12,14,16 is carried by an associated support bracket or frame
24,26,28 to rotate through an arc about a fixed axis such that the
upper end of each scoop remains positioned beneath the associated
gob discharge orifice, while the lower end of each scoop swings
through an arc adjacent to an associated array of troughs or chutes
30,32,34. The number of troughs in each array 30,32,34 is detenr~ined
by the number of sections 35 in the IS machine. The number of scoops
12,14,16, the number of orifices 18,20,22 and the number of trough arrays
30,32,34 are all determined by the number of molds or cavities in each
section 35 of the IS machine. For example, three gob orifices,
scoops and chute arrays are illustrated in FIG. 1 for use in connection
with a so-called triple-cavity IS machine in which each section 35
includes three parison molds 35a,35b and 35c. A typical IS machine
may include eight such machine sections 35, so that each chute array
30,32,34 would include eight individual chutes positioned for alignment
with the corresponding saoo~p 12,14,16, of which only three chutes are
illustrated in FIG. 1 for purposes of clarity. The general purpose
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of gob distribution system 10 is to deliver glass mold charges or
gobs to the three molds 35a,35b,35c simultaneously for each machine
section 35 in sequence. To the extent thus far described, system 10
is of generally conventional construction.
In accordance with the present invention, each of the scoop
supports 24,26,28 is coupled by an associated drive shaft 36,38,40 to
a gear box 42,44,46 (FIGS. 1 and 2) driven by an associated electric
servo motor 48,50,52. Each servo motor 48,50,52 reoeivesdrive signals
from a corresponding servo amplifier 54,56,58 under control of an
associated motion controller 60,62,64. A first position sensor R1,
such as a conventional resolver, is coupled to each servo motor
48,50,52 for providing to the associated motion controller 60,62,64,
an electrical signal indicative of angular position of the associated
motor drive shaft. A second position sensor R2, such as a conventional
a resolver, is coupled to each gear box 42,44,46 for providing to the
associated motion controller 60,62,64 a second electrical signal
indicative of absolute position of the associated scoop 12,14,16. The
several motion controllers 60,62,64 are coupled by a communications
link 66 to a supervisory controller 68. Supervisory controller 68
receives a synchronizing input from an infrared sensor 70 positioned
adjacent to a selected one of the gob orifices 13,20,22 (FIG. 1) to
provide a corresponding signal when a glass gob is discharged from
the orifice. Supervisory controller 68 is also connected to an
operator interface 72, such as a keyboard and screen, for receiving
calibration and adjustment inputs, etc., and providing output for
display to a machine operator. Supervisory controller 68 and motion
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controllers 60,62,64 also receive synchronizing master clock and master
reset inputs from IS machine 35,
In operation, each motion controller 60,62,64 receives from
supervisory controller 68 and stores in internal memory a table of
data indicative desired position profile 74 (FIGS. 3 and 4> at the
associated scoop. For example. FIG. 4 illustrates a profile 74 for
an eight-section machine in which each scoop is cycled through chute
positions 1,5,4,8,3,7.2 and 6 in a continuing sequence for
distributing glass gobs simultaneously to the three parison molds
of each machine section in that sequence. Within each motion
controller 60,62,64, the profile 74 for the associated scoop is compared
to the position feedback from the associated resolver R1, with the
difference or error generating an absolute torque command 76 (FIG.
3). This torque command is commutated at 78 for power phases A and
B applied to the associated amplifier 54 (or 56, 58). The torque
command for the third phase is calculated in the associated amplifier
as the sum of the torque commands for the first and second phases.
These torque commands are applied by the amplifier to the associated
servo motor to drive the gear box and scoop to the desired scoop
position.
The resolvers R2 indicate absolute position for each scoop.
This position information is employed during system initialization
to determine actual position of each scoop, which is fed to supervisory
controller 68. The supervisory controller may then command each
motion controller to move its associated scoop to a defined initial
or "home" position. After this initialization sequence, the absolute
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position output of resolvers R2 may be monitored periodically to
correct any drift in scoop position.
It will be readily appreciated that the electric motor and
motor control gob distribution system 10 illustrated in the drawings
represents a distinct advantage over the prior art gear transmission
drive arrangements discussed above. The several scoops 12,14,16 are
mechanically completely independent of each other, so that position
of each scoop may be calibrated and controlled completely
independently of all other scoops. For example, position of scoop 12
at any point in its profile 74 may be readily adjusted by means of
operator interface 72, supervisory controller 68 and motion controller
60 without in any way affecting motion or position at any of the
other scoops. Motion and profile of each scoop may be adjusted
during system operation. Scoops may be added, deleted or simply
rendered inoperative by addition or deletion of associated servo
motors and motion controllers etc. without requiring complete
replacement or major rework of a gear drive transmission. For
example. FIG. 2 illustrates addition of a fourth motion controller
80 with associated amplifier 82, motor 84, gear box 86 and scoop 88.
If the overall speed of the glass forming machine must be
increased, supervisory controller 68 may automatically reduce the
allowable time for motion of the various scoops, and adjust the
motion profiles accordingly so that the dwell times during which
each scoop is aligned with a chute remains constant. The same profile
74 would normally be used for each scoop, but a unique profile that
accommodates unique design considerations or minor dimensional
variations between or among chutes may be readily accommodated. The
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scoops would normally be synchronized to operate at the same time,
moving into and out of position at the same time. However, here
again differences may be readily accommodated by electronic adjustment
because each scoop is electronically controlled independently of the
other scoops. Scoop positions may be determined and set during
installation by moving the scoops into alignment with each of the
troughs in turn and storing the corresponding position information
in memory. The master clock and master reset signals from IS machine
35 are employed for primary synchronization purposes, with infrared
sensor 70 providing back-up.
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